Let me chime in here.
Doing this in a synthetic benchmark is totally unfair. It is cheating, as it artificially inflates scores in comparison to other cards, which render everything.
Now, is this cheating if done in GAME benchmarks like timedemos? Maybe yes, maybe no. I think if NV3x cards do the same thing when you're actually playing a game, then no, it's not cheating. Because it is representative of real world performance.
Looks like nvidia got something out of 3dfx after all. 3dfx's uber 1337 software HSR routines